Back when you learned to drive, you may have been instructed to keep your hands on the wheel at 10 o’clock and 2 o’clock. Of course, the older you got, the more likely that rule was relegated to the realm of “suggestion,” especially as the equipment in our cars—stereos, onboard navigation, even climate control—got more and more complicated. And of course, there’s the all too common sight today of someone speeding past you while chatting merrily away on his or her cell phone.

But if you’re a California resident, it’s time to hang up and drive. As of Tuesday, most drivers in the Golden State are prohibited from talking on their cell phone while driving unless they’re using a handsfree device, such as a Bluetooth headset.

The law aims to reduce the number of accidents that occur because people are distracted while talking on the phone, which some reports contend can be as dangerous as driving while intoxicated. Californians pulled over while using their cell phones without a handsfree device will receive a $20 fine the first time; the fine jumps to $50 for subsequent infractions.

There are some exceptions to the California law. Emergency personnel driving authorized vehicles in the course of their duties are exempt, as are commercial drivers (those with Class A or B licenses), though only until 2011.

Five other states—Connecticut, New York, New Jersey, Utah, and Washington (whose law also went into effect Tuesday)—currently ban handheld cell phone use while driving; Washington D.C. and the U.S. Virgin Islands have bans as well. Illinois, Ohio, New Mexico, Massachusetts, Michigan, and Pennsylvania have no statewide laws, but allow local jurisdictions to enforce restrictions at their own discretion, resulting in bans in cities such as Chicago, Cleveland, Santa Fe, and Albuquerque. In addition, New Mexico bans the use of cell phones while driving in state vehicles.

Several states have tried and failed to ban cell phones while driving, including Arizona, Kansas, Maryland, Nevada, Oklahoma, West Virginia, Wisconsin, and Wyoming. Others, such as Hawaii, Indiana, Nebraska, North Dakota and Texas, are still debating legislation. And a number of countries outside the U.S. have also enacted restrictions on the practice.

So what to do if you’re an iPhone user who simply must be on the phone while driving? Fortunately, there are a few options. The iPhone comes with a wired headset in the form of its earbuds—though, depending on the state and local laws where you live, wearing headphones while driving may be just as illegal as talking on the phone, so you may have to use only one earbud.

If the wired headset doesn’t cut it, the iPhone’s built-in Bluetooth feature supports the handsfree profile, allowing you to pair the phone with a compatible Bluetooth headset or the handsfree systems included in some cars, among them some Acura, BMW, and Lexus models. Of course, we recommend getting concrete information on compatibility from a manufacturer or dealer before rushing out to buy one on impulse.

Should you not quite be willing to splurge for a new car to feed your talking and driving habit, you might consider the far more economical solution of a Bluetooth headset. Apple produces its own Apple Bluetooth Headset for use with the iPhone, but most other headsets on the market should work fine, such as the popular Aliph Jawbone and Plantronics Voyager 520 (pictured above). iPhone Central is also working on a roundup of several Bluetooth headsets which we hope to bring you soon.

That’s not to say things are entirely rosy when it comes to using the iPhone without relying on your hands. While answering the phone with a Bluetooth headset or the included headphones is usually as simple as hitting a button, making calls is far more complicated. Unlike many common conventional phones, the iPhone doesn’t have voice-dialing support—you can’t say someone’s name and have the phone dial their number. And as sleek and intuitive as the iPhone’s multitouch interface is when you’ve got both hands free, its does tend to require more attention than your conventional cell phone, since it’s hard to operate by touch alone.

If none of the above quite appeal to you, there’s also this completely radical suggestion: try to avoid using your phone while driving period. That way you can eliminate one distraction and be absolutely sure you won’t be on the receiving end of a nasty fine.

Macworld editorial intern James Wickboldt contributed to this report.

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